The organization and management of collections of articles such as books, tapes, cassettes, and the like has been difficult when a large number of such articles is required to be maintained in such a manner that selected articles may be quickly located and retrieved. Requests for particular articles stored in large libraries are typically met by searching through an index, data base, or the like, determining the location within the library of a requested article from the data base or index, locating the particular cabinet or case, and shelf, in which the requested article is stored, and retrieving the article from the particular case or cabinet. In libraries containing large numbers of articles, multiple searches for requested articles during a work day can be tedious and time consuming. One form of library in which prompt location and retrieval of stored articles is of particular importance is that of libraries of magnetic tapes, associated with data processing centers. Such magnetic tapes may be in the form of open reel tapes or tape cartridges of various types. Large data processing centers sometime require libraries of thousands or even hundreds of thousands of magnetic tapes for use with a mainframe computer, and it may be necessary, in a typical work shift, to retrieve many requested tapes from the library and to load the tapes into appropriate tape drives interconnected with the computer. The tapes are normally coded with unique alphanumeric identification numbers, and a tape request will typically be in the form of a request for a tape having a specified identification number, to be loaded in a designated tape drive.
Because of the substantial capital investment and ongoing operating expenses associated with large data processing installations, it is of substantial importance that such tape requests be quickly and accurately met. Thus, it may be specified that responses to tape requests be completed in less than one minute, on average.